Treatment of underground formations



United- .StarS-.Pati 0.

. I I ""fzsos' ii, p TREATMENT or UNDERGROUND FORMATIONS A. Boyle; Norwood, :Pa.,- assignor ,to Sun: Oil

Commie,v h ad ph P zar rafi p of e JerSey-H No Drawing. Application May 2,1956

=Se'rial No. 582,066 p 6.Claims. (C1. 252 55 .l i Yent Qs-i1 S tqi h i e ms lt r ml mb r s d undtom i s fat t i im ose a l fi rating 'the-fiow of .liydrocarhons, from the formation into a production well. More" particularly, the; invention is concerned with the useofaliphatic arnines f e latively low molecular weight for treating form-ations t improve theflow of .hydrocarbonsztherethrough while-hindering the fiow of water. Y

It has been proposed heretofore to treat oil bearing sands with various aminecompoundsofrelatively high molecular weight to. facilitatetheproduction of oil from the formation. It is thoughtthat beneficial effects are obtained by such treatment due to chemi-sorption of the amine-on the sand surfaces,-whereby the sand is' rendered oleophilic or preferentially wettable by oil. This permits the oil to flow more freely through the formation while hindering the flow of water. In order to achieve this result, it has been considered heretofore that the amine employed should be of relatively high molecular weight so that the absorbed amine molecules will provide relatively large hydrocarbon groups that can function to alter the nature of the sand surfaces. Sand normally is hydrophilic, and it has been thought that the large hydrocarbon groups are necessary in order to have substantial effect in altering the character of the surfaces so as to make them oleophilic.

Amines which have been proposed heretofore for this purpose include such compounds as decylarnine, hexadecylamine, d-ioctylamine, octadecylamine, lauryl dimethylamine and docosylamine. Sruch compounds are soluble in hydrocarbons and can be introduced into the formation in the form of a solution in a suitable hydrocarbon material, such as kerosene, diesel oil or crude oil. They are, however, essentially insoluble in water. This is disadvantageous in that the treating compound cannot readi- 1y reach all sand surfaces in the zone being treated due to the presence of protective water films which act as barriers. The presence of water in the formation thus hinders the amine treating agent in contacting the sand surfaces and becoming absorbed thereon. This tends to reduce the effectiveness of the treatment, thereby necessitating the use of larger amounts of the treating solution or requiring the well undergoing treatment to be shut in for longer periods before production can be resumed.

I have now found that effective treatment of petroleumbearing formations to render the sands preferentially oil wettable can be acorn-plished by treating the formation with certain low molecular weight amines which are water soluble. According to the invention, straight chain aliphatic primary amines having 1-5 carbon atoms per molecule and having the amino group attached to a terminal carbon atom are employed to treat the formation and render its surfaces oleophilic. The amines specifically are methyl-amine, ethylamine, n-propylamine, n-butylamine and amylamine. All of these are highly soluble'in water and are capable of dissolving in and diffusing through water films present in the formation, th us facili-' tating contact of the amine with surfaces and promoting v 2,908,64 spammed 3 @1952 2 adsorption of the amine by the sand. Primary amines of low molecular weight which do not have '-the,'amino group attached to-a termianl carbon atom such as iso propylamine, sec-butylamine, ,tert-butylamine, 2-amino pentane and 3-aminopentane, while being soluble in water are not effective for thei-,present, purpose and are not withinthe scope ofthe invention. i The treat-mentofan oil well according to-the invention may be carried outby dissolving a minor amount of one or more of the amines as specified above in a suit-able hydrocarbon solvent,,su ch as kerosene, gas oil, crude oil or the like, and introducing thejs olution through the' borehole into the formation. Onlya small proportion, e.g. less than 5% of'the amine'need be: used in the solution for good results, although larger 'proportionsmaybeeinployed ifdesired. Generally it.is preferable that the amount of amine in the treating solution bev within the range of 0.Q52.0% byweight, since it has been found that suchsmall proportions can eifectivelyandeconomically be employed to achieve the desired results. 1 Asthe [solution of treating agent .flowsifrom the borehole into the formation being treated, the amine contacts the sand surfaces, both by direct contact of the hydrocarbon solution ofamine therewith and by. dissolutionof the low molecular weight amine in water films or channels and diffusion therethrough to the sand surfaces; I Adsorption of the amine on the sand changes the characterof ,the surfaces and renders thenr oleophilic When the well is subsequently put back into operation, the oil can pass more readily through the treated zone whereas the flow of water from farther back in the formation toward the borehole is retarded. The treatment thus effects an increase in the raito of oil to water produced from the Well.

The invention also is useful in treating natural gas wells to improve the flow of hydrocarbons into the well. All formations bearing natural gas, like those bearing heavier hydrocarbons, contain interstitial or connate water which tends to retard the flow of hydrocarbons.

' 6.5 C. or ethylamine having a normal boiling point of 16.6 C. may be introduced in gaseous phase into the well and thence into the formation. The amine will pierce the sheaths of interstitial water in the formation and be adsorbed on the sand surfaces to render them oleophilic. When the well is then allowed to flow, the pressure of the natural gas will force the displaced water into the borehole and open the channels for the flow of gas. The treatment thus effects an increase in the permeability of the sands to the hydrocarbon phase. Instead of adding the amine treating agent in gaseous form, a hydrocarbon solution of the amine as previously described may also be used in treating natural gas wells if desired.

For the purpose of illustrating the effectiveness of the invention, two comparative runs were made with silica cores, using n-butylamine as the treating agent in one case and isopropylamine in the other. In each run a specially designed flow cell for holding a silica core and flowing through it a hydrocarbon phase and a brine phase simultaneously under standardized constant head conditions was employed. The silica core in each case was made by compressing finely divided silica under a pressure of about 10,000 p.s.i.g. to form a core of about ID. and 2 /2" length. Permeabilities of the core to both the hydrocarbon and brine phases during and after treatment were determined.

In the run made according to the invention, kerosene and brine initially were fed to the'core under the conare not suitable stant head conditions; and it was found that the permeabilities of the core to the kerosene and to the brine were 2.5 and 1.0rnillidarcies, respectively. The ratio of kerosene to water passing through the core was 1.4 to 1. The core was then treated by continuing the two phase flow but'substituting for the plain kerosene a kerosenesolution containing 0.10% fn-butylamine. It was found that the permeability with respect to .the hydrocarbon phase increased to 9.3 millidarcies while that with respect to brine decreased to 015 millidarcy. Thereafter. the simultaneous flows of kerosene without the amine treating agent and of brine .were continued for. twenty days, without substantial change in the permeabilities to either phase. Theratio of kerosene to water passing through the core after the treating step was about .30 to 1.

The foregoing results illustratethe eflectiveness. of the primary amine treating agents herein specified "for. practicing the invention. By way of comparisona run was made under essentially identical conditions as described above but employingan amine in which the amino group is not attached to a terminal carbonatom, namely, isopropylamine; The core in this case initially had permeabilities to kerosene and to brine of 0.7 and 2.5 millidarcies, respectively, The treatment with isopropylamine had only a smalleflre'ct on each of these values although the overall effect was adverse. After ten days of treatment the permeability to theihydrocarbon phase had dropped to 0.3, whilethe permeability to brine had risen slightly to 2.9. indicates that amines in which the amino group is' not attached to a-tel minal carbon atom for practicing the invention.

Iclaim: V 1. Method of facilitating the flow of hydrocarbons e from an undergroundrformation containing hydrocarbons and water which comprises treating the formation with a straight chain aliphatic primary amine selected-from the group consisting of methylamine, ethylamine, n-propylamine, n-butylamine and amylamine to render surfaces of the formation oleophilic and increase the hy drocarbon permeability of the formation.

2. Method of treating an oil bearing formation containing water to facilitate the flow of oil which comprises introducing into the formation a hydrocarbon solution containing a'r'ninor amount of a straight chain aliphatic primary amine selected from the group consisting of rnethylamine, ethylamine, n-propylamine, n-butylamine and amylamine.

3. Method according n-buty-lamine. I

4. Method of treating a natural gas bearing formation containing water to increase the hydrocarbon permeability. of the formation which comprises introducing into the formation in gaseous phase a straight chain primary aliphatic amine" selected from the group consisting of methylamine, ethylamine, n-pro pylamine, -'n'-buty1amine n r m e-za 5. Mountedyaccording'to claim 4 wherein said amine is methylamine. I 7

6. Method "according to'cl'aim 4 wherein said amine is ethylamine.

to claim 2 wherein said mine is References'cited thefile of this patent UNITED STATES PATENTS 2,204,223 Lawton et al. June 11, 1940 

1. METHOD OF FACILITATING THE FLOW OF HYDROCARBONBS FROM AN UNDERGROUND FORMATION CONTAINING HYDROCARBONS AND WATER WHICH COMPRISES TREATING THE FORMATION WITH A STRAIGHT CHAIN ALIPHATIC PRIMARY AMINE SELECTED FROM THE GROUP CONSISTING OF METHYLAMINE AND AMYLAMINE TO RENDER SURFACES OF THE FORMATION OLEOPHILIC AND INCREASE THE HYDROCARBON PERMEABILITY OF THE FORMATION. 